1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device. More particularly, the present invention relates to a method of manufacturing an oxide layer.
2. Description of the Related Art
Currently, oxide layers are widely used in the semiconductor devices since the oxide layers have a relatively good insulating effect. Applications of oxide layers include an inter-metal dielectric layer between two interconnect layers, isolation structures, gate oxide, a dielectric layer between a floating gate and a controlling gate in an electrically erasable and programmable read-only memory (EEPROM) device, etc.
Conventional oxide layer on the rough surface of a polysilicon layer is formed by thermal oxidation. However the roughness of the polysilicon layer surface is determined by the accumulative directions of the polysilicon lattice during thermal oxidation process. Additionally, the range and the configuration of the polysilicon layer are affected by the temperature when the oxide layer is formed by thermal oxidation procedure. Therefore, it is difficult to produce a properly rough surface of the polysilicon layer.
Currently, the step that the oxide layer is formed on the rough surface of a polysilicon layer is usually present in the method of fabricating an EEPROM device. In order to increase the penetration ability of electrons, it is necessary to roughen the surface of the floating gate of the EEPROM device before the oxide layer between the floating gate and the controlling gate is formed. Because the rough surface of the floating gate can enhance the intensity of the local electric field, the penetration ability of electrons is increased.